The present invention relates in general to storage tanks, and, more particularly, to insulated storage tanks.
In the petroleum and chemical industries it is customary to store liquids and the like within large tank structures which are usually installed out in the open where they are exposed to the elements, both heat and/or cold. These storage facilities must be provided with a suitable insulating material so that the products in storage within the storage tanks may be kept at the desired temperatures. In previous storage tank insulation, it has been customary to apply some type of an insulating material exteriorly of the metallic tank structure and to securely bind the same thereto by the use of an adhesive or by circumferential bands extending completely around the outside diameter of the tank and secured in a fixed position. The manner of securing insulating panels to the exterior of a metallic storage tank is objectionable for the reason that the tank structure is oftentimes exposed to varying temperature gradients with the result that the metallic shell is caused to expand and contract due to such temperature variations. Obviously, if an insulating material has been applied to the exterior surface of such a tank as by adhesively securing the same thereto, the adhesive bond between the metallic shell and insulating material is caused to be broken due to such expansion and contraction with the result that the insulating material is separated from the metallic shell with resultant loss of insulation for the tank at such spots or areas. In instances where the insulating material is secured to the tank structure as by means of exteriorly extending circumferential bands, the bands are usually set to a pretensioned force at the time of installation of the insulating material and when, by reason of differing temperature gradients, the tank walls are caused to expand and/or contract, the bands, which are usually formed of metal, are incapable of further stretching to accommodate the expansion of the tank and insulating material thereon and will break or snap off, thus necessitating the repair or replacement of such bands. On the other hand, where the tank structure is caused to contract, the metallic bands lose their efficiency as holding means for the insulating material since the bands are not exposed to the temperatures within the tank which causes such contraction of the metallic tank.
There have been devices disclosed directed to overcoming problems associated with such storage facilities. One solution has been proposed in U.S. Pat. No. Re. 27,330, and other insulated tanks are disclosed in U.S. Pat. Nos. 3,010,599, 2,980,279, 4,146,952, 4,122,640, 4,044,517 and 3,993,213. Double wall tanks are disclosed in U.S. Pat. Nos. 3,612,332 and 3,935,957.
However, none of these known structures provides adequate support for tank insulation in all directions, that is both longitudinally and laterally of the tank. Furthermore, none of the known structures protects against gas movement through the insulation in a manner which is thoroughly effective.
Thus, there is need for a system of tank insulation which is securely supported in all directions, and which is effectively sealed against gas movement through that insulation.